WeatherTalk: Hurricanes begin as a complex of thunderstorms

When tropical storms become better organized, the system intensifies.

ISS hurrican isabel
Hurricane Isabel photographed from the International Space Station.
Credit: NASA
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FARGO — Tropical depressions, tropical storms and hurricanes all get their start as a complex of thunderstorms originating in the tropics, sometimes as far away as the coast of Africa). These "tropical waves" are often the precursor to further development. A tropical depression is a tropical wave that develops a center of low pressure, poorly organized and with winds of less than 40 mph. When the tropical depression intensifies beyond a sustained 39 mph wind, it is named a "tropical storm" and given a name — which will be discussed in tomorrow's piece.

When tropical storms become better organized, the system intensifies. Once the sustained winds reach 74 mph, the storm is upgraded to a hurricane. There are five categories of hurricane, with category 3, 4 and 5 being considered a "major hurricane." Category 5 hurricanes need winds of at least 157 mph, and some, like Hurricane Patricia in 2015, can reach sustained winds upwards of 215 mph.

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